I dont know... we never really woke him for a bottle, we just sort of gave it to him in his cot, and he would drink it whilst still being nearly asleep. I think theres a certain age though when that stops working, so maybe Callum is too old for that?
I wish I had some other suggestions, but all I know is that I always put it down to a growth spurt, as he would eat more during the day too, and it would usually only last for a few weeks. I hope you can figure something out though, goodluck!